This invention relates to an ice producing machine and a method that produces ice.
An ice producing machine generally has a condensing unit and an ice making assembly that operate together to produce and harvest ice. Ice making assemblies operate either in a batch mode or a continuous mode. In the batch mode, operation alternates between freeze and harvest cycles. In the continuous mode, operation constantly makes and harvests ice simultaneously. Continuous mode ice producing machines that make flaked or nugget ice forms are commonly known as flaker ice producing machines.
The ice making assembly of a flaker ice producing machine generally includes a cylindrical evaporator that has an external surface surrounded by tubes through which a refrigerant flows. The refrigerant is circulated by operation of a compressor. As the cylindrical evaporator is being chilled, water is applied to its internal surface so that ice forms thereon. A layer of the ice is removed and conveyed to a top of the evaporator by an auger. The ice is then pushed through a head that defines the ice form and dispensed to an ice bin.
The auger drive train includes an electric motor and a gear reducer. The motor has typically included a centrifugal switch that closes when the motor attains normal operating speed. Closure of the centrifugal switch actuates a relay that turns the compressor on to circulate the refrigerant. The centrifugal switch remains closed and the relay remains actuated until the motor stops rotating. When the motor does stop rotating, the centrifugal switch opens, the compressor relay is deactuated and the compressor is turned off.
The motor stops rotating when it is turned off intentionally, when there is a power failure or when motor loading becomes so great as to prevent rotation. Motor loading can be caused by a number of circumstances including motor or gear reducer failure, bearing failure or ice clogging in the evaporator due to over chilling. Generally, motor loading due to any of these circumstances will occur over a considerable amount of time before it becomes so great as to stop rotation. During this time, the ice producing machine may be extensively damaged. For example, continued operation of the compressor during heavy motor loading can cause evaporator mounting bolts to break, the cylinder to rotate and the refrigerant tubes to break or leak, thereby releasing the refrigerant.
The ice making assembly of a flaker ice producing machine also includes an ice bin into which the ice is conveyed and stored. A light detector is positioned to detect and provide a bin full signal voltage when the ice bin is full. The ice making assembly responds to the ice bin full voltage to stop making ice until the light detector provides a voltage that represents a bin not full condition. One prior art method of setting a threshold for the light detector calculated the threshold at 50% of the voltage developed by the light detector with only ambient light incident thereon. During ice making, the software interprets voltage above the threshold as the bin being full and voltage below the threshold as the bin being not full. For a bin not full condition, the emitter beam is fully incident on the light detector and the light detector voltage tends toward zero volt. However, during ice making, water drops can form on the light detector window and provide a degree of obscurity that can provide false readings. That is, the light detector develops voltages above the threshold when the bin is not full. These readings re interpreted by the software as the bin being full.
There is a need for an ice producing machine and method that turns off the compressor and ice making operation thereof before motor loading can result in damage to the machine or the need for service calls.
There is also a need for an improved light detector threshold setting technique that is not subject to faulty interpretation by the system software.
The present invention satisfies the aforementioned need with an ice producing machine and method that monitors current flow through the motor that drives the auger and turns off the motor and the compressor when a parameter proportional to the current flow exceeds a threshold that signifies a potential load problem. The method uses a three strike process by which the motor that drives the auger is subsequently turned on after a short wait. If the current flow parameter still exceeds the threshold, the motor is turned off a second time and then on again after a short wait. If the current flow parameter still exceeds the threshold, the motor is turned off a third time and the ice producing machine enters a wait status. If the current flow parameter is below the threshold, the three strike process is reset and the ice producing machine is free to perform normal ice making operations. Each time the motor is turned off an alert is signaled. If the motor is turned off a third time, the alert will remain on to alert the operator/owner that service is required.
The present invention also provides a threshold setting procedure for a light detector that detects ice bin full conditions. This procedure responds to an ambient light voltage produced by the light detector to set the threshold level of the detector to either of two levels dependent on the value of the ambient light voltage. If the ambient light voltage is less than a first value, the threshold is set to a fraction of the ambient voltage. If the ambient light voltage is equal to or greater than the first value, the threshold is set to the ambient voltage minus a fractional amount. For example, the first value may be about one volt, the fraction may be 0.75 and the fractional amount may be about 0.5 volt. In either case, the threshold is set near the ambient level, which results in higher thresholds than the prior art method, thereby avoiding the water drop obscurity problem.